Coursework 2: 2D Led Array
In this task, we assume that an 8×8 LED array is controlled by 2 words specified in led_array. Each
bit in this memory space controls the on/off state of one LED with 1 turns on an LED and 0 turns
off an LED. Each byte of the led_array maps to one row of LEDs and the least significant bit of this
byte controls the right-most LED of this row.
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 0
th byte
Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 1
st byte
. . . . . . . Bit 16 2
nd byte
. . . . . . . Bit 24 3
rd byte
. . . . . . . Bit 32 4
th byte
. . . . . . . Bit 40 5
th byte
. . . . . . . Bit 48 6
th byte
Bit 63 Bit 62 Bit 61 Bit 60 Bit 59 Bit 58 Bit 57 Bit 56 7
th byte
One example is shown below. 0x81 is the first byte of led_array, the first bit is 1 and the last bit is
also 1, this will turn on the top left and top right LEDs.
led_array DCD 0x00000081, 0x81000000
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
If there were issues found in this coursework specification after its initial release, it will be
updated and announced on LMO.
Task 1: (60%)
In this task, we assume that only one LED on the edge of this led array is turned on. Implement
the function “spin_single”, which rotates the position of the light-emitting LED clock-wise once.
For example, if the original state of led_array is:
led_array DCD 0x18666602, 0x00243C3C
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
After calling function “spin_single” once, led_array should become:
led_array DCD 0x18666601, 0x00243C3C
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
Calling it once more, led_array should become:
led_array DCD 0x18666700, 0x00243C3C
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
Calling it once more, led_array should become:
led_array DCD 0x18676600, 0x00243C3C
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
There are 4 important requirements/restrictions on your program:
1. Your function should not modify the state of any LEDs in the middle. Only the LEDs on the edge
can be changed.
2. You are not allowed to use DCD (or similar assembler directives like DCW or DCB) to declare
new memory blocks.
3. Your function must return to its caller when finished.
4. You should not assume a fixed initial position of the light-emitting LED on the edge. It may
appear at any position when spin_single is called.
Task 2: (40%)
Implement the function called “spin_multi”, which rotates light-emitting LEDs on the edge clockwise once. There’s no fixed pattern for light-emitting LEDs on the edge. Given the example state
of led_array below:
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
After calling spin_multi once, it should become:
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
Calling spin_multi again, it should become:
0
th byte
1
st byte
2
nd byte
3
rd byte
4
th byte
5
th byte
6
th byte
7
th byte
Just like task 1, There are 4 important requirements/restrictions on your program:
1. Your function should not modify the state of any LEDs in the middle. Only the LEDs on the edge
can be changed.
2. You are not allowed to use DCD (or similar assembler directives like DCW or DCB) to declare
new memory blocks.
3. Your function must return to its caller when finished.
4. You should not assume a fixed initial position of the light-emitting LED sequences on the edge.